[Function add]

1. Add leetcode solutions.

Author: Botao Xiao

README.md

@@ -335,6 +335,12 @@
 
 [187. Repeated DNA Sequences](https://github.com/Seanforfun/Algorithm-and-Leetcode/blob/master/leetcode/187.%20Repeated%20DNA%20Sequences.md)
 
+[189. Rotate Array](https://github.com/Seanforfun/Algorithm-and-Leetcode/blob/master/leetcode/189.%20Rotate%20Array.md)
+
+[190. Reverse Bits](https://github.com/Seanforfun/Algorithm-and-Leetcode/blob/master/leetcode/190.%20Reverse%20Bits.md)
+
+[191. Number of 1 Bits](https://github.com/Seanforfun/Algorithm-and-Leetcode/blob/master/leetcode/191.%20Number%20of%201%20Bits.md)
+
 ## Algorithm(4th_Edition)
 Reading notes of book Algorithm(4th Algorithm),ISBN: 9787115293800.
 All java realization codes are placed in different packages.

leetcode/189. Rotate Array.md

@@ -67,4 +67,28 @@ class Solution {
         }
     }
 }
-```
+```
+
+### 二刷
+1. 先计算余数。
+2. 保存从尾向前余数个个数。
+3. 将剩余的数向后以后。
+4. 最后将保存的数填充到数组的最开头。
+
+```Java
+class Solution {
+    public void rotate(int[] nums, int k) {
+        int len = nums.length;
+        int t = k % len;
+        int[] arr = new int[t];
+        for(int i = 0; i < t; i++){
+            arr[i] = nums[len - t + i];
+        }
+        for(int i = len - t - 1; i >= 0; i--){
+            nums[i + t] = nums[i];
+        }
+        for(int i = 0; i < t; i++)
+            nums[i] = arr[i];
+    }
+}
+```

leetcode/190. Reverse Bits.md

@@ -37,4 +37,21 @@ public class Solution {
         return result;
     }
 }
-```
+```
+
+### 二刷
+1. 唯一要注意的就是右移补零是>>>
+```Java
+public class Solution {
+    // you need treat n as an unsigned value
+    public int reverseBits(int n) {
+        int result = 0;
+        int ref = 1 << 31;
+        for(int i = 0; i < 16; i++){
+            result += ((n & (1 << i)) << (31 - i * 2));
+            result += ((n & (ref >>> i)) >>> (31 - i * 2));
+        }
+        return result;
+    }
+}
+```

leetcode/191. Number of 1 Bits.md

@@ -32,4 +32,20 @@ public class Solution {
         return count;
     }
 }
-```
+```
+
+### 二刷
+```Java
+public class Solution {
+    // you need to treat n as an unsigned value
+    public int hammingWeight(int n) {
+        int count = 0;
+        int cur = 1;
+        for(int i = 0; i < 32; i++){
+            if((n & (1 << i)) != 0)
+                count ++;
+        }
+        return count;
+    }
+}
+```